Aluminum vs Cast heads
05-16-2006, 02:16 PM
#1
Melting Slicks
Thread Starter
Aluminum vs Cast heads
Is there a really big performance difference (besides weight) in an aluminum head over a cast iron head?. Been looking at the Edlebrock BB oval heads for sometime...I have early 70's closed chambered 100cc heads (3931063) with bigger valves for a higher CR in my 454. Car is just a street toy..not a daily driver or serious race car. Advice is appreciated - should I keep the cast or spend the $$.
05-16-2006, 02:32 PM
#2
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If you get the exact same head design but one in cast iron and one in aluminum the cast iron head will put out more horsepower. To run aluminum you should run one point in compression higher to make up for the lost power.
The problem is alot of the better designed/flowing heads are only made in aluminum so you are stuck with choice.
The weight difference is really noticable when you are removing/installing the heads and leaning over the fender. Takes 2 to lift off the old cast iron heads but no problem installing the lighter aluminum alone.
The problem is alot of the better designed/flowing heads are only made in aluminum so you are stuck with choice.
The weight difference is really noticable when you are removing/installing the heads and leaning over the fender. Takes 2 to lift off the old cast iron heads but no problem installing the lighter aluminum alone.
05-16-2006, 02:39 PM
#3
Le Mans Master
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The performance difference per say- is the fact you can run higher compression w/ the alum heads because they're more efficient in getting rid of heat.
Not to mention- they are a hellovalot easier to clean up and match the ports.
And it's only money...I haven't seen a funeral yet where there was a U-haul trailer behind the hearse!!!
I went w/ aluminum!!!
Richard
Not to mention- they are a hellovalot easier to clean up and match the ports.
And it's only money...I haven't seen a funeral yet where there was a U-haul trailer behind the hearse!!!
I went w/ aluminum!!!
Richard
05-16-2006, 04:25 PM
#4
Burning Brakes
I really like the Idea of having 50 pounds removed off of the front of the car. Cast iron heads weigh about 50 pounds a peice, aluminums only weigh around 25 pounds. If you make an effort to make your car even lighter doing things like mini starters, electric fans and aluminum water pumps, you can take even more weight off of the car. I can definitly tell a difference when I have another passenger in the car or a full tank of gas. Think of the difference you can make by taking that much weigh off the front of the car.
05-16-2006, 04:57 PM
#6
Le Mans Master
Originally Posted by norvalwilhelm
If you get the exact same head design but one in cast iron and one in aluminum the cast iron head will put out more horsepower. To run aluminum you should run one point in compression higher to make up for the lost power.
The problem is alot of the better designed/flowing heads are only made in aluminum so you are stuck with choice.
The weight difference is really noticable when you are removing/installing the heads and leaning over the fender. Takes 2 to lift off the old cast iron heads but no problem installing the lighter aluminum alone.
The problem is alot of the better designed/flowing heads are only made in aluminum so you are stuck with choice.
The weight difference is really noticable when you are removing/installing the heads and leaning over the fender. Takes 2 to lift off the old cast iron heads but no problem installing the lighter aluminum alone.
05-16-2006, 06:01 PM
#7
Safety Car
An average engine, even those heavily breathed on, will not see a performance difference in identical heads other than different materials. There has been a lot of theory on the performance difference as far as thermal efficiency, detonation resistance, compression increase and so on. The theories have a basis but the real application is being ignored for the bottom line. Like aluminum heads can run more compression. Well, when they had very thin decks, you could or should, but alloy heads now have much thicker decks and denser casting. You can run more compression because of the combustion chamber design.
Unless you are a NASCAR or Pro Stock engine builder and can get to that 2hp/ci threshold, you will not see a performance increase based only upon the casting material.
Most of the gains being attributed to the alloy belong instead to the advances in combustion chamber and port improvements.
Alloy's big advantage is that they are easy to repair and is why they became popular. The weight savings is also a huge advantage as long as you follow through on the diet.
Most people use alloy heads because there are not a lot of iron heads with the same design features...and they're sexy because aluminum was always an exotic alloy for American iron. Pedestrian for the European makes, but rare for America.
Unless you are a NASCAR or Pro Stock engine builder and can get to that 2hp/ci threshold, you will not see a performance increase based only upon the casting material.
Most of the gains being attributed to the alloy belong instead to the advances in combustion chamber and port improvements.
Alloy's big advantage is that they are easy to repair and is why they became popular. The weight savings is also a huge advantage as long as you follow through on the diet.
Most people use alloy heads because there are not a lot of iron heads with the same design features...and they're sexy because aluminum was always an exotic alloy for American iron. Pedestrian for the European makes, but rare for America.
05-16-2006, 06:51 PM
#8
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CNC Machined heads will be better than factory casting....the uniformity of the ports and chamber will make for better efficiency across the board. If you like Iron.....go for the 990 heads a bigger cam and better intake (square port). If you want to stay with ovals get the Edlebrock heads and use your factory intake.....I would still up the cam. It all boils down to what are trying get for your money? And How much Money!
05-16-2006, 08:22 PM
#9
Melting Slicks
Originally Posted by norvalwilhelm
If you get the exact same head design but one in cast iron and one in aluminum the cast iron head will put out more horsepower. To run aluminum you should run one point in compression higher to make up for the lost power.
The problem is alot of the better designed/flowing heads are only made in aluminum so you are stuck with choice.
The weight difference is really noticable when you are removing/installing the heads and leaning over the fender. Takes 2 to lift off the old cast iron heads but no problem installing the lighter aluminum alone.
The problem is alot of the better designed/flowing heads are only made in aluminum so you are stuck with choice.
The weight difference is really noticable when you are removing/installing the heads and leaning over the fender. Takes 2 to lift off the old cast iron heads but no problem installing the lighter aluminum alone.
There is a difference. Bumping up the compression on the aluminum will gain back what is lost. Look at the whole package and decide what parts go with what parts. If going aluminum, bump up the compression to make up for the loss in hp.
05-17-2006, 08:00 AM
#10
Melting Slicks
Thread Starter
Was debating the purchase because I have a real nice set of cast heads that have just been reworked, bowls opened, bigger valves that I have not yet installed....got about $400.00 machine work in those. I didn't know if the breathing would be better on the Edelbrocks vice the closed chambered to make up for the CR loss. From your opinions, if weight is not a big concern ....then I should just stick with the cast.
05-17-2006, 11:31 AM
#11
Norval pretty much covered it.
There is a difference. Bumping up the compression on the aluminum will gain back what is lost. Look at the whole package and decide what parts go with what parts. If going aluminum, bump up the compression to make up for the loss in hp.
AFAIK the loss is due the the better thermal conductivity of aluminium removing heat from the chambers, so bumping up the CR compensates for the loss of power due to this.
Given the choice between iron & alloy I'd go for alloy as it's lighter (as well as improved port designs, etc). Dropping that much weight at a stoke can be a lot easier than making the additional power needed to accelearte that weight. Also less weight means better braking, steering, handling, tire life(?!), etc. Given the choice between buying a set of alloy heads & using a set of decent iron ones already paid for, I'd go for the iron ones
As well as all the above advantages/disadvantages, I finally got 2 engines side by side that were almost identical, apart from one having an ally head & the other having an iron head. Stock uses an ally head but due to "user error" one engine no longer had a serviceable ally head. It was then fitted with an iron head from a previous model, with the head machined by an engineer (with a good reputation) so that the chamber size/shape were as close to the ally one as possible, squish band & ports were modded, etc, etc. The first thing noticed was that it suffered from terrible pinging on unleaded fuel so the CR was dropped down by changing the pistons, meaning, unfortunately, that the 2 engines aren't quite the same anymore. Having heard both engines run I can say that the one fitted with the iron head sounds better, it's a deeper, more mellow tone. The engine with the alloy head also sounded a bit more rattly from the valve gear, so the iron head could possibly be soaking up a lot of the noise (or perhaps the valve gear is in better condition & there's less backlash in the gears, etc).
Anyway, iron heads seem to make an engine sound nicer than alloy heads, not that it really matters, but it's kinda interesting. Possibly? At least for 30 secs or so..... I'll get me coat
Originally Posted by mandm1200
There is a difference. Bumping up the compression on the aluminum will gain back what is lost. Look at the whole package and decide what parts go with what parts. If going aluminum, bump up the compression to make up for the loss in hp.
Given the choice between iron & alloy I'd go for alloy as it's lighter (as well as improved port designs, etc). Dropping that much weight at a stoke can be a lot easier than making the additional power needed to accelearte that weight. Also less weight means better braking, steering, handling, tire life(?!), etc. Given the choice between buying a set of alloy heads & using a set of decent iron ones already paid for, I'd go for the iron ones
As well as all the above advantages/disadvantages, I finally got 2 engines side by side that were almost identical, apart from one having an ally head & the other having an iron head. Stock uses an ally head but due to "user error" one engine no longer had a serviceable ally head. It was then fitted with an iron head from a previous model, with the head machined by an engineer (with a good reputation) so that the chamber size/shape were as close to the ally one as possible, squish band & ports were modded, etc, etc. The first thing noticed was that it suffered from terrible pinging on unleaded fuel so the CR was dropped down by changing the pistons, meaning, unfortunately, that the 2 engines aren't quite the same anymore. Having heard both engines run I can say that the one fitted with the iron head sounds better, it's a deeper, more mellow tone. The engine with the alloy head also sounded a bit more rattly from the valve gear, so the iron head could possibly be soaking up a lot of the noise (or perhaps the valve gear is in better condition & there's less backlash in the gears, etc).
Anyway, iron heads seem to make an engine sound nicer than alloy heads, not that it really matters, but it's kinda interesting. Possibly? At least for 30 secs or so..... I'll get me coat
05-17-2006, 11:47 AM
#12
Race Director
Originally Posted by Bismarck
On a big block engine the weight difference is between 70 -75 pounds, not 50.
Actually 70 lbs and right off the front end too. And a copper shim gasket is preferred as it mates with the aluminum better as those used on the L88`s as the OEM gasket. 
05-17-2006, 12:51 PM
#14
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Last month Hot Rod did a test where they took identical heads, one made in aluminum, and the exact same head in cast iron.
Running on the dyno, there was absolutely no difference in the horsepower made. They thought there would be more horsepower with the cast iron heads, there wasn't.
Now I don't know which material I should be looking at???
Running on the dyno, there was absolutely no difference in the horsepower made. They thought there would be more horsepower with the cast iron heads, there wasn't.
Now I don't know which material I should be looking at???
05-17-2006, 01:02 PM
#15
Race Director
Originally Posted by Garrett1972
Last month Hot Rod did a test where they took identical heads, one made in aluminum, and the exact same head in cast iron.
Running on the dyno, there was absolutely no difference in the horsepower made. They thought there would be more horsepower with the cast iron heads, there wasn't.
Now I don't know which material I should be looking at???
Running on the dyno, there was absolutely no difference in the horsepower made. They thought there would be more horsepower with the cast iron heads, there wasn't.
Now I don't know which material I should be looking at???
05-17-2006, 01:19 PM
#16
Melting Slicks
Thread Starter
I'm a little hesitant to go alum and lose the compression ratio I have now with the 101cc closed chambers (approx 10.25) with flat top pistons. Don't want to change pistons to get the CR back up.......
05-17-2006, 01:46 PM
#17
Drifting
Lighter weight, easier to port, first time you drop a valve or have shrapnel in a cylinder that damages your head, the replacement cost of an iron head will be more than aluminum would have cost in the first place. Ask me how I know 
From now on, unless absolutely prohibited, I'll have aluminum on all my engines.
From now on, unless absolutely prohibited, I'll have aluminum on all my engines.
05-17-2006, 09:30 PM
#18
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Originally Posted by L88Plus
Lighter weight, easier to port, first time you drop a valve or have shrapnel in a cylinder that damages your head, the replacement cost of an iron head will be more than aluminum would have cost in the first place. Ask me how I know From now on, unless absolutely prohibited, I'll have aluminum on all my engines.
From now on, unless absolutely prohibited, I'll have aluminum on all my engines.
05-18-2006, 10:01 AM
#19
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The difference in weight and handling is worth it. I just put aluminum heads, intake and dewitts aluminum radiator in my 71 LS5 and it drives like a different car.
If you want to keep the compression ratio you have now and want to go aluminum then look for a head that has similar cc's... Edelbrock has a set that are similar (cc wise) and I am using them on my engine.
I have a .060 over 454 with flat top TRW forged pistons... gives me about 9.22 to 1 compression with a .016 deck hieght and a .039 gasket thickness.
The Edelbrock part number 60499 for the complete head.
Chamber Size 100cc semi-open chamber heads
Intake Port Size 290cc
Valve Sizes (in/ex) 2.19"/1.88"
Part #60499
Check out Edelbrock, s website for the rest.
If you want to keep the compression ratio you have now and want to go aluminum then look for a head that has similar cc's... Edelbrock has a set that are similar (cc wise) and I am using them on my engine.
I have a .060 over 454 with flat top TRW forged pistons... gives me about 9.22 to 1 compression with a .016 deck hieght and a .039 gasket thickness.
The Edelbrock part number 60499 for the complete head.
Chamber Size 100cc semi-open chamber heads
Intake Port Size 290cc
Valve Sizes (in/ex) 2.19"/1.88"
Part #60499
Check out Edelbrock, s website for the rest.
05-18-2006, 12:22 PM
#20
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As stated above, with aluminum, you can add 1 more point of compression over iron before pinging. A side benifit is that you can run a bigger cam with that extra compression